JP2005109509A - Method and device for printing pattern on light sensitive surface by using maskless lithography system having spatial optical modulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate a stitch error in a print pattern generated near the stitch line between adjacent exposure zones, when using a spatial optical modulator (SLM) for printing a pattern onto a light sensitive surface. <P>SOLUTION: At least two exposure regions are prescribed on the light sensitive surface. The exposure regions overlap along each edge in the exposure regions, and an overlap zone is formed between the exposure regions. At least two exposure regions are exposed for printing an image to the exposure regions. In this case, exposure is made over the entire overlap zone. After that, the exposure in the overlap zone is attenuated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for printing a pattern on a light sensitive surface using a maskless lithography system having a spatial light modulator (SLM), and a maskless lithography system having a spatial light modulator (SLM). A computer readable medium having one or more sequences of one or more instructions for execution by one or more processors to implement a method for printing a pattern on a light sensitive surface.

  A print pattern in a general-purpose maskless lithography tool is formed by a series of exposures or shots. Each shot is obtained from an image of a spatial light modulator (SLM) projected onto the surface of a light sensitive surface such as a wafer substrate. As a result, a predetermined dose amount, that is, a predetermined irradiation amount from the light source is deposited in a predetermined exposure zone on the surface. An exposure zone is created when the substrate surface is illuminated by a flash of light from a light source. When the pattern crosses the exposure boundary of a single spatial light modulator SLM, the exposure is stitched along the adjacent boundary to form one complete pattern.

  Seaming errors or stitching errors in the printed pattern occur near such boundaries between adjacent exposure zones due to both exposure geometric misalignment and optical interference. . In general, stitch errors occur in a printed pattern due to a spatial misalignment of the exposure zone on the wafer from the expected position. Even in cases where alignment is perfect, stitching errors can be caused by optical effects. Even small shot spatial misalignments can result in significant perturbation of the printed pattern near the stitch line.

  The cause of the optical action is that the dose distribution in each exposure zone results in exposure with partially coherent light. Since two adjacent exposure zones are exposed at different points in time, the exposure is practically incoherent, which causes unwanted optical effects.

  Accordingly, an object of the present invention is to compensate for a print pattern stitch error that occurs in the vicinity of a stitch line between adjacent exposure zones.

According to the present invention, this problem is defined by defining two or more exposure areas on the photosensitive surface and overlapping the exposure areas along their individual edge portions so that the exposure areas Forming an overlap zone, exposing two or more exposure areas and printing an image there, so that the exposure covers the entire overlap zone,
This is solved by attenuating the exposure in the overlap zone.

  Next, further features and advantages of the present invention, and structures and operations of various embodiments of the present invention will be described in detail with reference to the drawings.

  Next, the present invention will be described in detail with reference to the drawings showing embodiments according to the present invention. Other embodiments are possible, and various alternative embodiments are possible within the scope of the present invention. Therefore, the present invention is not limited to the following description, and is defined only by the description of the scope of claims.

  It will be apparent to those skilled in the art that the present invention described below can be implemented in a wide variety of forms of hardware, software, firmware and / or entities shown in the figures. All actual software code is not a limitation of the present invention, with the dedicated hardware being controlled to implement the present invention. Therefore, the operation and behavior of the present invention will be described on the assumption that each embodiment can be modified if there are individual levels shown here.

  FIG. 1 shows a block diagram of a maskless lithography system configured in accordance with one embodiment according to the present invention. In FIG. 1, a maskless lithography system 100 shows a control system 102. The control system 102 includes a computer processor, a memory, and a user interface that allow a user to enter input data for instructing the maskless lithography system 100 to generate a print pattern.

  The control system 102 is connected to a pulsed light source 104, which generates a pulse of light from a light source, such as an excimer laser or some other suitable pulsed illumination mechanism. The pulsed light source 104 is connected to a beam relay system 106, which is typically an anamorphic system, which includes a series of lenses, thereby providing the pulsed light source 104. A desired numerical aperture is formed in the light beam generated by. The pulsed light source output from the beam relay 106 is imaged on the programmable array 108.

  Programmable array 108 is configured to receive image pattern data 110 representing a desired lithographic pattern and reflect light representing the image to projection optics (PO) 109. The pattern data 110 is also known as mask layout data. The light reflected from the programmable array 108 passes through the PO 109 and is incident on the substrate 112. The function of the projection optical system is to 1) generate an image of the object on the substrate, and 2) reduce the image as compared with the size of the object. A pattern representing the image data 110 is then imaged onto a light sensitive surface 112, such as a wafer substrate, which is scanned at a constant speed. As will be appreciated by those skilled in the art, the image to be projected onto the light sensitive surface 112 is contained in the programmable array 108 and can be changed by the user via the control system 102.

  The programmable array 108 may comprise a spatial light modulator SML or any other suitable micromirror array. Stated as background, the spatial light modulator SML is an array of a number of individually controlled pixels (also referred to as SLM elements). Each pixel can change the optical properties in a controllable manner, thereby modulating the field in the object plane. A typical SLM has a plurality of square pixels arranged in a rectangular array, each pixel being capable of changing only one of a plurality of parameters characterizing optical properties within a predetermined range. Capability (one-parametric local modulation).

For example, an existing SLM has 16 × 16 mm ² tiltable mirrors arranged in a 2040 × 512 array and operates at a refresh rate of 1 kHz. The light modulation schemes implemented in various SLMs can be classified as transmittance modulation, light deflection modulation, phase shift modulation, defocus modulation, and / or combinations of these various modulation formats.

  FIG. 2 shows a perspective view illustrating a more detailed appearance of a maskless lithography system, such as system 100 of FIG. In the case of FIG. 2, system 200 includes SLM 202, PO 203, and substrate 204 with a light sensitive surface. The SLM 202 has a mirror element 206 that reflects the light pulse 208 onto the substrate 204 in the two-dimensional exposure region 210. The light pulse 208 is used to generate a pattern 212 in the exposure area 210.

  As a background, a print pattern in a maskless lithography tool is formed by a two-dimensional exposure or shot sequence. Each of the two-dimensional shots is derived from a single SLM image, which is projected onto the wafer surface, resulting in a deposition of dose within a given exposure zone. In addition, each exposure is formed by a single light pulse from a pulsed light source. Since the two-dimensional exposure zones are stitched together at the edges, the stitching operation is very critical. A shift in one exposure zone on the order of a few nanometers can cause pattern errors along the edges, which are clearly noticeable and damage features in the pattern. As shown in FIG. 3, a single exposure can be performed with multiple passes over one substrate surface.

  FIG. 3 shows the formation of a single pattern feature, which extends beyond the borders or stitch lines of adjacent exposure zones. In the case of FIG. 3, the exposure zones 300 to be stitched include exposure zones 301, 302, and 304. Each of these exposure zones is created by the deposition of a dose on a light sensitive surface caused by a single light pulse from an illumination source such as the pulsed light source 104 of FIG. That is, during a single pulse, a photosensitive surface, such as substrate 204, is moved a predetermined distance, resulting in a deposition of dose in each of zones 301, 302, and 304.

  A stitch line 306 is formed by an adjacent boundary between the exposure zones 302 and 304. A pattern feature 308 is formed in the exposure zones 301, 302, and 304, which is located beyond the stitch line 306. Due to the partial dose distribution within each exposure zone being the result of exposure with partially coherent light, optical effects or distortion of the feature 308 may be caused. Since two adjacent exposure zones 302 and 304 are then exposed at different times, these exposure zones are practically incoherent.

  FIG. 4 shows the stitch failure near the stitch line in the desired uniform pattern for the scenario of coherent illumination. An example of coherent irradiation was used for the purpose shown in the drawing. This is because coherent illumination is considered to cause the most serious stitching errors in the printed pattern. However, the present invention is not limited to such application examples.

  According to FIG. 4, graph 400 shows that a uniformly bright field has been combined with two exposures stitched at the origin. The first exposure 402 is obtained from a pixel to the right of the origin in the object plane set to an absolutely bright state, whereas the object plane field to the left of the origin is zero. The resulting relative intensity distribution or relative dose change in the imaging plane is a well-known diffraction limited imaging in the half plane.

  The second exposure 404 is a mirror image of the exposure 402 centered on the origin. As can be seen immediately from this graph, the relative dose value (or relative imaging intensity) at the origin for both exposures is 1/4 in the case of coherent illumination. The combination of right edge exposure 402 and left edge exposure 404 results in a relative local dose value of ½ along the stitch boundary 407. The combination of exposures at stitch line 407 with a relative local dose value of ½ causes stitch artifacts or stitch errors 408.

  In practice, stitch artifacts such as stitch artifact 408 will interfere with the form of features formed across a stitch boundary such as boundary 407 (eg, feature 308 in FIG. 3). This type of disturbance to the form is that variations occur with respect to the width of the lines used to form the printed pattern.

  FIG. 5 shows the effect of stitch error on line variations in the absence of stitch error compensation techniques. More specifically, FIG. 5 depicts a test case showing a stitch failure represented by a separate dark line. In the case of FIG. 5, the exposure 502 shown as an example includes a horizontal dark line 503 separated on a light background, which is approximately 2000 nanometers (nm) long (˜˜). 9λ / NA), where λ is the wavelength of light and NA is the numerical aperture. Horizontal dark lines 503 are formed using tiltable mirror pixels in the object plane.

According to the example of FIG. 5, the size of each pixel scaled to the image plane is given by the formula M * L = 40 nm
Can be obtained. Here, M is a magnification and L is a pixel length.

Line 503 is formed by two adjacent horizontal arrays of mirrors each tilted by α ₀ = λ / (2 * L) and (−α ₀ ), where α is the tilt angle is there. These rows of pixels behave almost as absolutely dark pixels. The background is bright and is formed by pixels with a flat mirror.

  The pattern forming line 503 is exposed by three exposures, ie 502, 504, 506, as described with reference to FIG. Exposure 502 occurs during the first pass of the substrate, exposing all lines 503. Exposures 504 and 506 are two successive exposures that occur during the second pass of the substrate. Each of the two exposures 504 and 506 exposes one half of the dark line 503, respectively. Dose distributions 504a and 506a associated with exposures 504 and 506, respectively, are shown near the stitch line, which is obtained from each of the three exposures. Also shown is a sum 508 of three exposures 502, 504, 506, which includes an underexposed area along the stitch line 509a.

  A graph 510 shows a change in the line width near the stitch line 509a. In the example of FIG. 5, the line width was calculated using the image intensity threshold, resulting in a line 512 of 70 nm. As shown in graph 510, the change represented by line 514 extends to +25 nm.

  As shown in the examples of FIGS. 4 and 5, an abnormality that significantly deteriorates the print pattern due to a stitch error may occur. However, according to the present invention, the effect caused by such a stitch error is compensated. Several techniques are provided for doing this.

Stitch Compensation without Overlap FIG. 6 illustrates one technique 600 for compensating for the effects of stitch errors. More specifically, the technique of FIG. 6 provides stitch error compensation that does not utilize exposure area overlap. According to technique 600, auxiliary features can be added during the second pass of substrate surface exposure. In the application of the present invention, the auxiliary feature is added during the second pass, but any subsequent pass is used as long as the pass to which the auxiliary feature is added does not have a boundary at the same location as the feature. Also good.

  The auxiliary features are added to the mask layout or pattern data (eg, pattern data 110 in FIG. 1) input to the SLM to generate a print pattern. In the example of FIG. 6, auxiliary features are added to the pattern data in order to thicken the line in the second pass at the same position corresponding to the previous pass to compensate for the effects of stitch errors.

  According to FIG. 6, during the first exposure (ie during a single light pulse from the illumination source), a line is generated on the photosensitive surface of the substrate. The line includes a left segment 602 and a right segment 604, both of which are formed during the first pass. The left segment 602 and the right segment 604 form a line 606 having a stitch failure (constriction) 608 beyond the stitch line 609. To compensate for stitch disturbance 608, auxiliary features 610 are added to the pattern data associated with the generation of line 606.

  During the second pass of the substrate, auxiliary features 610 form a bulge at stitch line 609 in line 612 formed in the object plane. Although a line 612 with auxiliary features 610 is formed in the object plane, it is combined with line 606 to form a single line 614 in the object plane. Line 614 is free of stitch failure 608. In other words, the swelled portion represented by the auxiliary feature 610 compensates for the constriction or stitch failure 608 caused by the first pass. More generally, if the exposure zone from one pass is shifted relative to the exposure zone from another pass, the feature is compensated for a pass that is not affected by the stitch line and the stitch failure affecting the feature. Can be used to

  During scanning, exposure is performed in the adjacent exposure zone. That is, the wafer is scanned once and then moved to produce another exposure zone adjacent to the previous zone. Subsequent pulses arrive and subsequent exposure zones are formed. At that time, a stitch error may occur and be detected in the exposure zone. The process of detecting or predicting stitch errors in the exposure zone can be implemented using several techniques well known to those skilled in the art.

  Further, pattern preprint analysis is performed using image modeling using a modeling tool and a simulation tool, for example. By using such a modeling tool or a similar tool, it is possible to simulate the occurrence of a stitch error at a stitch boundary. The simulation can be performed a priori or in real time. Accordingly, techniques such as technique 600 of FIG. 6 can be implemented a priori or in real time.

  Another technique for compensating for stitch errors that does not utilize exposure area overlap is active compensation. With active compensation, exposure is performed by butting (ie, without overlap) and the state of the SLM pixels near the stitch line can be adjusted. That is, SLM pixels near the stitch line can be selected to compensate for the stitch failure.

  For example, as a result of underexposure due to the edge effect, the width of the print line may increase near the stitch line due to stitch failure. For this reason, by using the SLM pixel in a brighter state near the stitch line, the effect of increasing the line width can be suppressed. Thus, the state of the four SLM pixels adjacent to the stitch line can be adjusted according to a proportional amount to compensate for the widening of the print line width. Nonetheless, adjusting a small number of pixels does not always fully compensate for the stitching effect, but uses a larger number of pixels near the stitch line while calculating and adjusting the state by solving the inverse problem. As a result, appropriate compensation can be achieved.

  By adding compensation data to pattern data (eg, pattern data 110), pixel state calculations can be adjusted so that the desired pattern is printed by the pixel. The calculation of the pixel position is required so that the position of the stitch line is taken into account. By determining the pixel position, the exposure areas separated by the stitch lines are also exposed in different shots. Since exposure is performed with different shots, no coherence occurs between fields in the exposure. However, during active compensation, partial coherence occurs within each exposure based on the predetermined illumination mode.

  FIG. 7 is a flowchart illustrating an example method 700 for implementing the technique 600 of FIG. According to one embodiment, method 700 is performed by system 200 described above, but is not necessarily limited to such a configuration. According to FIG. 7, the first exposure is performed on the light sensitive surface according to the predetermined image data (step 702). This first exposure takes place during the first pass through the substrate surface, thereby forming a first image in one substrate area. According to step 704, image defects are identified within an area in the first image. The image data is then adjusted to compensate for the identified image defects (step 706). Further, during the second pass at step 708, a second exposure is performed on the light sensitive surface according to the adjusted image data.

Overlapping Exposure Zones with Attenuation FIG. 8 illustrates another technique 800 for compensating for step impairment effects. The technique 800 utilizes overlap of exposure zones, which results in attenuating the aerial image within the overlap region. In short, according to technique 800, a small overlap of exposure zones is used to compensate for stitching disturbances in the printed pattern that occur near the stitch line. The overlap area near the stitch line receives extra dose due to the extra exposure and aerial image attenuation is performed to compensate for such extra exposure. This attenuation can be performed either actively or passively.

  Active attenuation is based on dynamically adjusting the pixel state of the SLM array to provide attenuation in the overlap zone. Such active attenuation allows consideration of illumination mode, width, overlap geometry, specific patterns printed across overlap zones, as well as other factors.

  On the other hand, passive attenuation uses hardware changes associated with the SLM to perform the attenuation. Non-limiting methods of achieving passive attenuation include pre-processing and deforming the apodized aperture, defocus / field stop and SLM elements.

Apodized aperture The apodized aperture can be inserted in front of the object or in the intermediate image plane. This aperture has a variable transfer characteristic near the edge of the SLM array or its intermediate image, which ensures the attenuation of the aerial image. In order to compensate for the extra exposure in the overlap zone, it is advantageous to perform apodization near the vertical leading or trailing edge. The expression representing the change in transfer characteristics can be made to depend on specific irradiation conditions (which gives better stitch irradiation conditions). Furthermore, this equation can be a general equation that functions reasonably well over a wide range of irradiation conditions (eg, linear change in intensity transfer characteristics). Such an expression is derived from the prior art.

  Apodization may be passive (using an apodized aperture), active (adjusting the pixels of the SLM array near the stitch line), or a combination of the two. Passive apodization can be performed in the object plane or (intermediate) image plane.

Defocus / Field stop Defocus / field stop is an alternative to an apodized aperture, where a slightly defocused aperture can be used, or a mask plate is placed in front of the SLM.

Pre-processed deformation Based on pre-processing and deforming the SLM element in the overlap zone, the pixels that enter the overlap zone are pre-set to ensure the desired attenuation of the aerial image. It is to be transformed into.

  An example of pre-fabricating and deforming an SLM element is the use of tilting and pistoning of individual mirrors in the SLM array to provide micromirrors in the overlap zone relative to the SLM array. It is to change the reflectance of the surface. Such changes may be discontinuous (a constant reflectivity within each mirror, but varies from mirror to mirror), or may be continuous. Any modulation principle can be utilized (without using a micromirror) to change the reflectivity for the SLM array. For example, within the overlap zone, the pixels of the SLM array that utilize changes in transfer characteristics can be pre-processed such that the maximum transfer characteristics in their brightest state change as desired.

Yet another example of pre-processing and deforming an SLM element is to modify the discontinuous state of the SLM element or pixel in an embedded manner. This deformation envisages that the discontinuous state of the SLM element within the overlap zone (eg tilting of the tiltable micromirror) is deformed or compared to the discontinuous state of other SLM elements. It is shifted. Such a built-in deformation technique is another example of passive attenuation and can be applied to an SLM using some modulation scheme. FIG. 8 shows an example of the above-described active attenuation. . Specifically, FIG. 8 illustrates a technique that uses overlap of exposure zones to attenuate an aerial image using an active attenuation approach. According to FIG. 8, the exposures 502, 504, 506 shown in FIG. 5 are reanalyzed applying an active attenuation approach. In this case, the display 800 is formed by combining exposures 502, 504, and 506. For illustrative purposes, exposures 504 and 506 overlap by a width of 10 pixels to produce feature 802 within overlap zone 804. Within the overlap zone 804, linear attenuation of the object plane field is performed according to one of the passive attenuation techniques described above. After utilizing active attenuation, the resulting image 807 is generated by combining exposures 502, 504, 506. Graph 808 shows the improvement realized by reducing the change in line width. In particular, the graph 808 can reduce the line width change 810 associated with the line 512 shown in FIG. 5 from 25 nm to less than 5 nm (shown in FIG. 5).

  FIG. 9 is a flowchart illustrating an example of a method 900 for performing active attenuation of the aerial image in the overlap region. According to method 900, two or more exposed areas on the light sensitive surface are defined (step 902). These exposed areas overlap along the individual edge portions, thereby forming an overlap between the areas. In step 904, two or more exposure areas are exposed and an image printed thereon, with the exposure spreading through the overlap zone. Next, as shown in step 906, the exposure that occurred within the overlap is attenuated.

Utilizing Overlap Without Explicit Attenuation FIG. 10 illustrates a technique 1000 that uses overlap to compensate for stitch faults without explicit attenuation. This technique 1000 is an example of an approach that uses overlap without explicit attenuation. More specifically, the technique 1000 forms a stitch line that vibrates or swings along the stitch boundary. In other words, overlap zones are used to create stitch boundaries whose direction changes in a zigzag pattern or some other way.

  According to technique 1000, the exposure zones are overlapped. And within this overlap zone, only one of the two overlapping pixels carries the pattern. Other overlapping pixels are turned off. Thus, the resulting printed pattern is between two overlapping exposure zones, and the effective boundary between these two adjacent exposure zones is, for example, a “toothed” line or other abrupt rocking Allocate to some line. Such oscillating lines provide a spatial averaging of stitch faults and thus reduce the effect of the print pattern.

  The technique 1000 of FIG. 10 is an example of a swinging stitch line approach. According to FIG. 10, overlapping exposure zones 1002, 1004, 1006 are used to form print features 1005 along stitch zone 1007. However, in the technique 1000, the selected pixel is activated (from the pixels used to generate the overlapping exposures 1002, 1004, 1006) and the energy corresponding to the stitching fault is spatially averaged. It becomes. A zigzag pattern 1009 is generated by this spatial averaging. For example, within exposure zone 1004, selected (overlapping) pixels from a set of overlapping pixels represent zone portions 1004a, 1004b, 1004c. These selected pixels are then energized such that the pattern used to form feature 1005 is generated only from the pixels associated with exposure 1004 in one shot.

  Similarly, selected overlapping pixels that produce exposed portions 1006a, 1006b, 1006c from exposure 1006 are used to form other segments of the pattern. When exposures 1004 and 1006 are combined, exposure 1008 is formed, which has stitch artifacts that are substantially reduced within overlap region 1010. An alternative to this is to selectively turn on / off selected pixels from the pixel set to form an overlapped exposure, and some other such as a checkerboard pattern 1020 as depicted in FIG. 10A. A pattern can be formed.

  For example, overlapping pixels can be distributed between each exposure in a checkerboard pattern with white (on) pixels belonging to one exposure and black (off) pixels belonging to the other exposure. In this case, a higher spatial frequency is used than the oscillating boundary (if the pattern is properly selected, this spatial frequency can also be changed across the overlap zone), so a better stitch Can produce.

  In the case of FIG. 10 and FIG. 10A, the exposure zones are overlapped, and only one of the two overlapping pixels within the overlap zone bears the pattern. The other overlap pixel is turned off. Thus, a print pattern is distributed between two overlapping exposures, and the print pattern is preferably distributed between these exposures at a relatively high spatial frequency. Furthermore, because of the overlapping exposure, there is no need to form a connecting boundary that swings between the two exposures.

  FIG. 11 illustrates a method 1100 for implementing the present invention shown in FIG. In the case of FIG. 11, two or more exposure areas are defined within a predetermined area on the substrate surface. Each region corresponds to a selected pixel of the SLM (step 1101). In step 1102, an overlap region is formed between two or more exposure regions, the overlap region being defined by individual overlap edges in the exposure region. Furthermore, the overlapping edges correspond to overlapping pairs of pixels selected from each region. In step 1104, the pixels in each pair are alternatively activated so that only one of the pixels in the pair is used for patterning.

  By appropriately selecting the overlap width (without attenuation), stitch faults can be compensated. In any irradiation mode, matching (exposure with zero overlap) results in underexposure along the stitch line (for example, in coherent irradiation, the dose along the stitch line is 50% of the non-stitching value). Is). On the other hand, overexposure of the dose along the stitch line results from a fairly long overlap without attenuation (over several times λ / (M * NA)). If properly chosen between the two extremes, an accurate dose can be received at one precise position in the stitch line, thereby compensating for the fault near the stitch line.

  Overlap with a field stop close to the image plane will also reduce stitch / edge effects. In this case, the exposure zones are overlapped and the field stop is placed very close to the image plane, so that by this field stop the part of the image in the overlap zone most affected by the edge effect (the outer part of the SLM image). Is blocked. To ensure that the edge effect can be blocked by the field stop, the width of the exposure zone should be sufficiently wide (>> (λ / (M * NA)). The modulated pixels can be modulated to compensate for extra edge effects left in the image passing through the field stop.

  As a result, the image that reaches the image plane has substantially zero edge effects or very little edge effect there, and the stitching can be performed by matching the two images.

  An example of an overlap with a field stop is as follows: Separate lines across the stitch boundary are printed, and the pixels blocked by the field stop form an extension of the image of the line on the field stop. If the width of the blocked pixel layer is large enough (if it is much larger than (λ / (M * NA)), a single exposure that forms a half line image results in a half with sharp edges. The reason for this is that the edge-smearing effect is blocked by the field stop, so that if the second half of the line is imaged in the same way, the two images are matched. The stitch can be executed.

  The non-essential additional factors described below will also affect the effect of stitch failure.

Image smear Image smear due to wafer movement during exposure is an additional phenomenon that affects the effects of stitch failure. According to the exposure mechanism in the maskless lithography tool, the exposure can be performed by a short laser pulse executed on a wafer moved at a constant speed. Such an exposure mechanism causes image smearing in the direction of motion.

  The duration of the laser pulse must be small enough for smears to not have a significant effect on the printed pattern. For typical scan speeds and laser pulse durations, the smear effect should not exceed a few nm. This effect can be compensated for by synchronizing the laser pulses. At the same time, such smears can be advantageous if they naturally reduce stitching defects that occur near stitch lines perpendicular to the scanning direction.

Laser Pulse Jitter Laser pulse jitter is another factor that will affect the effect of stitch failure. For the exposure scenario described in the previous paragraph, the laser pulse may arrive too early or too late (laser jitter phenomenon). The characteristic size of the laser pulse jitter is 3σ = 10 ns (nsec). As a result of such a delay or advance, the exposure position on the wafer resulting from this laser pulse may shift in the wafer scanning direction or in the opposite direction. Any of these small ones can cause spatial misalignment of the stitched exposure, and this misalignment contributes to stitch failure (although exposure misalignment caused by other causes). . However, the stitch compensation technique shown in the present invention can be used to compensate for the effects of laser pulse jitter.

  As described above, the present invention can be implemented in hardware, or can be realized as a combination of software and hardware. Thus, the present invention can be implemented in a computer system or other processing system environment. An example of this type of computer system 1200 is shown in FIG.

  Computer system 1200 is provided with one or more processors, such as processor 1204. The processor 1204 is connected to a communication infrastructure 1206 (eg, a bus or network). As for the computer system of this embodiment, various software implementations will be described. After reading this description, it will be apparent to one skilled in the art how to implement the invention using other computer systems and / or computer architectures.

  The computer system 1200 includes a main memory 1208, preferably a random access memory (RAM), and an auxiliary storage device 1210 can also be provided. The auxiliary storage device 1210 may be provided with, for example, a hard disk drive 1212 and / or a removable storage drive 1214 such as a floppy disk drive, a magnetic tape drive, and an optical disk drive. The removable storage drive 1214 reads from or writes to the removable storage unit 1218 in a well-known manner. The removable storage unit 1218 is a floppy disk, magnetic tape, optical disk, etc., which is read and / or written by the removable storage unit 1214. Obviously, the removable storage unit 1218 comprises a computer usable storage medium having stored computer software and / or data.

  According to alternative embodiments, auxiliary storage device 1210 may include other similar means that allow computer programs or other instructions to be loaded into computer system 1200. Examples of such means include a removable storage unit 1222 and an interface 1220. Examples of such means may include a program cartridge and cartridge interface (which is used in video game devices), a removable memory chip (such as EPROM or PROM) and a corresponding socket, and a removable storage unit. Other removable storage units 1222 and interfaces 1220 that allow software and data to be transferred from 1222 to computer system 1200 may be included.

  Computer system 1200 may also include a communication interface 1224. Communication interface 1224 allows software and data to be transferred between computer system 1200 and external devices. Examples of the communication interface 1224 include a modem, a network interface (such as an Ethernet card), a communication port, a PCMCIA slot, and a PCMCIA card. Software and data transmitted via communication interface 1224 take the form of a signal 1228 that can be an electronic signal, an electromagnetic signal, an optical signal, or other signal receivable by communication interface 1224. These signals 1228 are supplied to the communication interface 1224 via the communication path 1226. Communication path 1226 carries signal 1228, which may be implemented using wires or cables, fiber optics, telephone lines, cellular telephone lines, RF links, and other communication channels.

  The terms “computer-readable medium” and “computer-usable medium” are used herein to refer to removable media drive 1214, a hard disk embedded in hard disk drive 1212, and media in general such as signal 1228. It is done. These computer program products are means for supplying software to the computer system 1200.

  Computer programs (also referred to as computer control logic) are stored in the main memory 1208 and / or the auxiliary storage device 1210. Computer programs can also be received via communication interface 1224. According to such a computer program, the computer system 1200 can implement the present invention described so far when executed.

  Specifically, the computer program enables the processor 1204 to perform the process of the present invention when executed. For example, according to one embodiment of the present invention, a process or method performed by a signal processing block consisting of an encoder and / or decoder can be implemented by computer control logic. Where the present invention is implemented using software, the software can be stored in a computer program product and loaded into the computer system 1200 using the removable storage drive 1214, hard disk drive 1212 or communication interface 1224. be able to.

CONCLUSION According to the present invention, several unique approaches are provided that compensate for the effects of stitch errors that may occur near stitch lines in a maskless lithography pattern. These approaches include: a) a technique that does not use overlap of exposure areas, b) a technique that uses overlap and attenuation, and c) a technique that uses overlap without explicit attenuation. These approaches, either alone or in combination, reduce stitch defects, optical anomalies, and other effects that otherwise enter the lithographic pattern printed on the light sensitive surface.

  So far, the present invention has been described using the functional constituent units exemplified for the execution of specific functions and the relationship between those functions. The boundaries of these functional structural units have been arbitrarily defined for convenience of explanation. Alternative boundaries may be defined as long as certain functions and their relationships are properly executed.

  Thus, any alternative boundary is within the scope of the present invention. Those skilled in the art will appreciate that these functional units are realized by analog and / or digital circuits, discrete components, application specific integrated circuits, firmware, processors executing appropriate software, etc., and combinations thereof. be able to. Accordingly, the scope of the present invention is not limited to the above-described embodiments, but is defined only by the following claims and their equivalents.

  The foregoing description of the specific embodiments shows all of the general features of the invention, and those skilled in the art will depart from the general outline of the invention without undue attempt. Rather, these specific embodiments can be readily modified and / or matched for various applications. Accordingly, such alignment and modifications are intended to be within the spirit and scope of the disclosed embodiments based on the teachings and instructions of the present invention. Of course, the expressions and terms used here are used for the purpose of explanation and are not intended to be limiting. The terms and expressions in the specification of the present invention refer to the teachings and instructions of the present invention described above. However, it should be interpreted by those skilled in the art.

1 is a block diagram illustrating a maskless lithography system constructed and arranged in accordance with one embodiment of the present invention. It is a perspective view which shows exposure of a photosensitive surface. It is a figure which shows the deposition of the dose amount in a some exposure zone. It is a graph which shows the stitch failure near the stitch line in a desired uniform pattern. It is a figure which shows the effect | action of the stitch disorder | damage | failure in the separated dark line. It is a figure which shows an example of the technique which compensates a stitch failure without using the overlap of an exposure zone. It is a flowchart which shows an example of the method of implementing the technique shown in FIG. It is a figure which shows an example of the technique which compensates a stitch fault by performing attenuation using the overlap of an exposure zone. It is a flowchart which shows an example of the method of implementing the technique shown in FIG. It is a figure which shows an example of the technique which produces | generates the pattern of the type which rocks without performing explicit attenuation | damping using an overlap, and compensates a stitch failure. It is a figure which shows a mode that the checkerboard type pattern is produced | generated in the technique shown in FIG. It is a flowchart which shows an example of the method of implementing the technique shown in FIG. It is a block diagram which shows an example of the computer system which can implement this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Maskless lithography system 102 Control system 104 Pulsed light source 106 Beam relay 108 Programmable array 109 Projection optical system 110 Pattern data 112 Substrate 202 Spatial light modulator 203 Projection optical system 204 Substrate with photosensitive surface 206 Mirror element 208 Optical pulse 210 Exposure area 212 Pattern 300, 301, 302, 304 Exposure zone 306, 407 Stitch line 408 Stitch failure

Claims (15)

In a method of printing a pattern on a light sensitive surface using a spatial light modulator (SLM),
Defining two or more exposure areas on the photosensitive surface and overlapping the exposure areas along their individual edge portions to form an overlap zone between the exposure areas;
Expose two or more exposure areas and print an image there so that the exposure spans the entire overlap zone;
Attenuating exposure in the overlap zone,
A method of printing a pattern on a light sensitive surface.   The method according to claim 1, wherein a laser dose is applied in the exposure.   The method of claim 1, wherein each exposure region corresponds to one irradiation source pulse.   The method of claim 1, wherein active attenuation is performed in the attenuation step.   5. The method of claim 4, wherein in the active attenuation step, the pixels in the spatial light modulator are dynamically adjusted to compensate for defects in the image.   The method of claim 1, wherein passive attenuation is performed in the attenuation step.   7. The method of claim 6, wherein the passive attenuation step is a function of at least one of the group consisting of apodized aperture, defocusing, aperture / field stop, and pre-processing deformation of the spatial light modulator pixel.   The method of claim 1, wherein the attenuation step is a function of at least one of the group consisting of illumination mode, overlap zone size and image size. In an apparatus for printing a pattern on a light sensitive surface using a spatial light modulator (SLM),
Means are provided for defining two or more exposure areas on the photosensitive surface, the exposure areas overlapping along their individual edge portions and overlapping zones between the exposure areas. Formed,
Means are provided for exposing two or more exposed areas and printing an image thereon, the exposure extending over the entire overlap zone;
Means for attenuating exposure in the overlap zone is provided,
A device for printing patterns on light sensitive surfaces.   The apparatus according to claim 9, wherein a laser dose is applied by the exposure unit.   The apparatus of claim 9, wherein each exposure region corresponds to one illumination source pulse.   The apparatus of claim 9, wherein active attenuation is performed by the attenuation means.   The apparatus of claim 9, wherein at the active attenuation, pixels in the spatial light modulator are dynamically adjusted to compensate for defects in the image.   The apparatus of claim 9, wherein the attenuating means performs passive attenuation. One or more sequences of one or more instructions for causing one or more processors to perform a method for printing a pattern on a light sensitive surface using a spatial light modulator (SLM) In a computer readable medium holding
When the instructions are executed by one or more processors, by one or more processors,
Two or more exposure areas are defined on the photosensitive surface, the exposure areas overlapping along their respective edge portions to form an overlap zone between the exposure areas; ,
Exposing the two or more exposed areas and printing an image thereon to expose the entire overlap zone; and
Attenuating exposure within the overlap zone;
Is executed,
A computer-readable medium.